The present invention relates to an ink jet recording head in which a piezoelectric vibrator of a longitudinal vibration mode is used as a driving source, and more particularly to a structure of an elastic plate which receives a pressure due to a displacement of a piezoelectric vibrator, and also to a method of producing such a plate.
In order to improve the recording density, the pitch of nozzle opening rows tends to be reduced. To comply with this tendency, a single crystal silicon wafer is isotropically etched, and a nozzle plate and an elastic plate which are produced another method are fixed to the etched wafer, thereby configuring a channel unit. A displacement of a piezoelectric vibrator is transmitted to the channel unit so as to produce a pressure in a pressure generating chamber, and an ink droplet is ejected from a nozzle opening by the pressure.
When pressure generating chambers are arranged in high density, each of the pressure generating chambers has a very small width. In order to cause the whole of the longitudinal direction of a pressure generating chamber to be efficiently deformed, therefore, a configuration is employed in which a convex portion, or a so-called island portion that elongates in the longitudinal direction of the pressure generating chamber is formed on the surface of the elastic plate, and the displacement of the piezoelectric vibrator is transmitted via the island portion to a wide region of the elastic plate sealing the pressure generating chamber.
It has been proposed that a polymer film or a metal thin plate is used as such an elastic plate, a metal plate member, for example, a stainless steel plate which has a relatively large thickness so as to ensure the rigidity of the elastic plate is laminated onto the surface of the elastic plate, and the stainless steel plate is etched, thereby forming an island portion which transmits a displacement of a piezoelectric vibrator to the whole of a pressure generating chamber, and a diaphragm portion which is elastically deformed by the displacement of the island portion to change the capacity of the pressure generating chamber (W093/25390).
However, this proposed configuration has the following problem. The coefficient of thermal expansion of the plate member serving as the elastic plate, particularly a polymer film is largely different from that of the metal plate for ensuring the rigidity. Furthermore, heat applied during the production process causes polymer materials to shrink. During the process of producing the channel unit, therefore, the plate member is flexurally deformed and a positional error occurs between the plate member and a channel forming substrate.